Poem:
The sequence leads you there
The "shift" is not that rare
It is ancient, you will see
Jupiter is the key
14 15 92 65 35 89 79 ??
OGSULLOIOGRREYSGXZ
Hint
Complete the number sequence and find out how it will help you encode the letters
Big Hint
The number sequence is well known, the cipher was established by a Roman guy